Weighing apparatus

Abstract

High-speed weighing apparatus in which the weighing platform responds to the pressure of an object thereon to produce an undamped oscillatory vertical motion indicative of the mass of the object on the platform. The platform is supported on a vertically-movable upright column, which in turn is spring-supported on a frame primarily by means of a flexure pivot support arrangement near its bottom end, which provides spring support for the platform and column to permit the vertical motion indicative of weight; it is also supported by another support arrangement operating on an upper portion of the column nearer the platform, for preventing tilting of the column without interfering with its vertical motion or with the weighing process. The second or upper support arrangement preferably comprises a horizontal flexible rod, secured at one end to the frame and at its other end to the upper part of the column.

What is claimed is: 
     
       1. In weighing apparatus of the class comprising object-receiving means for receiving objects to be weighed, a frame, resilient support means connected between said frame and said object-receiving means for providing spring mounting of said object-receiving means on said frame, said object-receiving means being adapted to move vertically with substantially undamped simple harmonic motion in response to the placement thereon of each of said objects in a manner determined by the spring characteristics of said resilient support means and the mass of said each object, and means for enabling sensing of the vertical displacement, velocity and acceleration of said each object on said object-receiving means to produce signals representative of the mass of said each object, the improvement wherein: said resilient support means comprises flexure pivot means mounting a first portion of said object-receiving means on said frame and resiliently supporting the major portion of the weight of said object-receiving means and of said objects to be weighed, and cantilevered spring means secured to and extending substantially horizontally between said frame and a second portion of said object-receiving means spaced vertically from said first portion, for restraining said object-receiving means against lateral motion thereof, said spring means being longitudinally rigid but transversely resilient along the vertical direction to accommodate said vertical motion of said object-receiving means without substantial vertical restraint thereof.   
     
     
       2. The apparatus of claim 1, wherein said frame and said spring means have substantially the same temperature coefficient of expansion. 
     
     
       3. The apparatus of claim 2, wherein said frame and said spring means are of stainless steel. 
     
     
       4. The apparatus of claim 1, wherein said frame is a massive weldment of stainless steel. 
     
     
       5. The apparatus of claim 4, wherein each of said flexure pivots means comprises outer casing means and flexure springs secured to said outer casing means, said outer casing means and said flexure springs being of stainless steel. 
     
     
       6. The apparatus of claim 1, wherein said flexure pivot means comprises linkage means, a first portion of which is pivotably mounted for rotation about a first horizontal pivot axis in said frame and a second portion of which is pivotably mounted for rotation about a second horizontal pivot axis in said first portion of said object-receiving means, said flexure pivot means producing torsional spring restraint about each of said pivot axes to provide said resilient support. 
     
     
       7. The apparatus of claim 6, wherein a part of said linkage means extends on the opposite side of said first pivot axis by a distance greater than the spacing between said first and second pivot axes, whereby said part of said linkage means provides an amplified and reversed version of the vertical motion of said object-receiving means. 
     
     
       8. The apparatus of claim 1, wherein the dimension of said spring means along the direction from said frame to said second portion of said object-receiving means is large compared with the vertical dimension thereof. 
     
     
       9. The apparatus of claim 8, wherein said spring means comprises a rod-like member of spring material. 
     
     
       10. The apparatus of claim 9, also comprising filamentary means extending substantially horizontally from said second portion of said object-receiving means to said frame at an angle to said rod-like member. 
     
     
       11. The apparatus of claim 10, wherein said filamentary means comprises filaments secured to and extending substantially horizontally between said object-receiving means and said frame. 
     
     
       12. The apparatus of claim 11, wherein said filaments extend collinearly with each other in opposite directions from said object-receiving means substantially at right angles to said rod-like member. 
     
     
       13. The apparatus of claim 12, wherein each of said filaments is smaller in cross-section and of smaller spring constant than said rod-like member. 
     
     
       14. In weighing apparatus of the class in which objects to be weighed are delivered along an object-flow direction successively onto and from a weighing platform which responds to the placement of an object thereon to produce a detectable substantially undamped simple harmonic vertical motion thereof representative of the mass of the object on the platform, said platform being mounted on vertically-movable upright columnar means which is supported on a frame by first and second support means in a manner to permit said substantially undamped simple harmonic vertical motion; said first support means comprising linkage means a first portion of which is pivotable mounted for rotation about a first horizontal pivot axis in said frame, a second portion of said linkage means being pivotably mounted for rotation about a second horizontal pivot axis in a first portion of said columnar means, and flexure pivot means associated with said linkage means for exerting a restoring torque about at least one of said pivot axes to provide spring support for said columnar means and platform; said second support means being connected to a second portion of said columnar means between said platform and said first portion of said columnar means to restrict lateral motion of said columnar means while permitting said vertical motion thereof; and means for enabling the sensing of the vertical displacement, velocity and acceleration of said object when placed on said weighing platform to produce signals representative of the mass of said object; the improvement wherein said second support means comprises cantilevered spring means extending substantially horizontally and radially of said columnar means and secured to said frame and to said second portion of said columnar means, said spring means being longitudinally rigid but transversely resilient in the vertical direction to accommodate repeated up-and-down motion of said columnar means.   
     
     
       15. The apparatus of claim 14, wherein said flexure pivot means exerts a restoring torque about both of said pivot axes. 
     
     
       16. The apparatus of claim 14, wherein the vertical spring restraint provided by said spring means is small compared with that provided by said flexure pivot means. 
     
     
       17. The apparatus of claim 15, wherein said frame comprises a unitary welded stainless steel structure to which are secured the radially-outward end of said spring means and the frame-fixed portion of said flexure pivot means, said spring means being also of stainless steel. 
     
     
       18. The apparatus of claim 17, comprising first and second filamentary members of lighter gauge than said spring means, said first and second filamentary members extending radially outwardly and collinearly from opposite sides of said columnar means, and each secured at one end to said columnar means and at its other end to said stainless steel structure, said columnar means also being of stainless steel. 
     
     
       19. The apparatus of claim 14, wherein the spring constant of said flexure pivot means is large compared with that of said spring means. 
     
     
       20. The apparatus of claim 19, wherein the spring restraint of vertical motion of said columnar means by said flexure pivot means is at least an order of magnitude greater than the spring restraint of vertical motion of said columnar means by said spring means. 
     
     
       21. The apparatus of claim 14, wherein said spring means comprises rod means secured at one end to said frame and at its other end to said columnar means. 
     
     
       22. The apparatus of claim 21, comprising a first substantially horizontal filamentary member secured at one end to said frame and at its other end to said second portion of said columnar means, and extending substantially at right angles to said rod means; and a second substantially horizontal filamentary member secured at one end to said frame on the opposite side of said columnar means from said first filamentary member and at its other end to said columnar means, said second filamentary member extending substantially collinearly with said first filamentary member and substantially at right angles to said rod means. 
     
     
       23. The apparatus of claim 22, wherein said rod means and said first and second filamentary means comprise the sole lateral support at said second portion of said columnar means. 
     
     
       24. The apparatus of claim 22, wherein each of said filamentary members has a tensile strength small compared with that of said rod means.